Use Of Acid Catalysts Research Articles

Electrochemical Synthesis and Reactivity of Three-Membered Strained Carbo- and Heterocycles.

Three-membered carbocyclic and heterocyclic ring structures are versatile synthetic building blocks in organic synthesis with biological importance. Moreover, the inherent strain of these three-membered rings leads to their ring-opening functionalization through C->C, C->N, and C-O bond cleavage. Traditional synthesis and ring-opening methods for these molecules require the use of acid catalysts or transition metals. Recently, electro-organic synthesis has emerged as a powerful tool for initiating new chemical transformations. In this review, the synthetic and mechanistic aspects of electro-mediated synthesis and ring-opening functionalization of three-membered carbo- and heterocycles are highlighted.

Selective Addition of Aniline to a Cage-opened Diketo Anhydride Derivative of C60

Abstract The nucleophilic addition of aniline was examined using a diketo cage-opened C60 derivative possessing an acid anhydride moiety. While the imination occurred at the 1,4-dicarbonyl moiety, the aminalization dominantly proceeded on the anhydride moiety in the presence of zinc(II). The thus formed aminal was thermally converted into acid anhydride while it could be transformed into corresponding isoimide by the use of acid catalyst. The introduced aniline moiety significantly perturbed the orifice size so that the insertion/escape dynamics of a water molecule were substantially restricted.

Central Composite Design of Biodiesel Production from Waste Cooking Oil using Tympanotonus fuscatus (Periwinkle) Shells as Catalyst

Biodiesel has been generally accepted as an environmentally – safer alternative to fossil based fuels. However, concerns of the cost of production, use of acid catalysts leading to corrosion, and recovery of homogenous catalyst remain. This study therefore seeks to optimize the transesterification process parameters in the conversion of waste cooking oil (WCO) using waste Tympanotonus fuscatus shell (WTFS). The catalysts were characterized using XRD, FTIR, and XRF. Temperatures ranging from 30°C to 90°C, catalyst loading from 1 to 10% by weight, and reaction durations from 30 to 180 minutes were examined for the transesterification technique. The physiochemical properties of the waste cooking oil revealed a high acid value (10.02mgKOH/g), kinematic viscosity of 13.30 mm2/s, pour point, 156oC, flash point of 104oC, Calorific value of 34.78 MJ/kg, carbon content of 2.65% m/m, among other parameters while the GCMS analysis indicated the presence of C16 to C21. The biodiesel however showed an acid value of 0.416 mgKOH/g, viscosity of 4.638 mm2/s, pour point of 0.3oC, flash point of 104oC, calorific value of 40.17 MJ/kg, and carbon content of 0.019% m/m which were in agreement with the EU and American standards. The elemental composition and crystalline structure of the catalyst revealed a considerable concentration of CaO, MgO, Al2O3, SiO2, and other metal oxides. The CCD approach used to design the experiments was significant (p <0.0001) and the biodiesel synthesis which resulted in a maximum yield of 91.70% was obtained with 5.5% WFTS, 105 minutes of reaction time, 65 oC, and a 1:7 oil–Methanol ratio. The operating parameters of temperature (p <0.0001), catalyst load (p = 0.00713), and time (p = 0.0288) all had significant effects on biodiesel yield; however, temperature had a stronger influence than the other process variables. The ANOVA results showed that the factors were extremely significant while Fit statistics and model comparison revealed a coefficient of determination of 97.66%, with the predicted value of 84.68% and the adjusted value of 95.00%. The biodiesel produced met the biodiesel standards.

Plasma-assisted catalytic route for transesterification reactions at room temperature

Biodiesel has been currently obtained from the transesterification reaction of vegetable oils, including residual oil as waste cooking oil (WCO), and usually in the presence of a catalyst. Advanced methods, such as plasma, have been studied to produce biodiesel since it allows for a milder conditions, mainly by decreasing both reaction temperature and time of production. The objective of this work is to investigate the plasma-assisted catalytic route for the monoesters transesterification reactions. H3PMo and NaOCH3 were used as acid and basic catalysts, respectively. The batch plasma reactor used in this work was composed by a borosilicate glass tube with concentric electrodes, in which ethyl acetate and methanol were feed. The effects of the plasma associated with both acid and basic catalysts were investigated in the ambient temperature and atmospheric pressure. In general, plasma-assisted catalytic routes showed higher ethyl acetate conversions, when compared to the routes with no plasma under the same experimental conditions. For example, the ethyl acetate conversion increased from 38% to 77% when plasma is assisting the acid catalytic reaction during 90 min. This level of conversion is comparable with values achieved for the reaction in the presence of basic catalyst without plasma, although in a shorter time of reaction. The synergistic effect between the plasma and the catalysts provided an increase in the reaction rate constants, and high ethyl acetate conversions in shorter reaction times. These findings indicate the plasma-assisted catalyst routes as promising for the production of biodiesel under room temperature, especially for the production from waste oils, which requires the use of acid catalysts and usually under extreme conditions.

Esterification Reaction of Glycerol to The Derivatives Catalyzed by Amberlyst 36

Several studies reported the use of acid catalysts of esterification of glycerol to acetin derivatives and amberlysts are no exception. However, among these strong sulfuric acid catalysts, amberlyst 36 is still rarely used and hence challenging to investigate. This study aimed to determine the yield and the selectivity of the esterification reaction of glycerol into acetine derivatives using a 5% of solid catalyst amberlyst 36 at a temperature of 90°C in a reflux system. The conversion value resulting from the reaction was 80.74%, with a selectivity value of 6.8% for triacetin. FTIR and GC-MS data support the monoacetin and triacetin structures. The findings indicate that the simple method and easily obtained catalyst can produce a high yield of acetin derivatives. This method is still possibly optimized to perform maximum yield with high selectivity.

Simultaneous upgrading of biomass-derived sugars to HMF/furfural via enzymatically isomerized ketose intermediates

BackgroundRecently, exploring fermentative or chemical pathways that convert biomass-derived sugars to fuels/chemicals has attracted a lot of interest from many researchers. We are investigating a hydrocarbon pathway from mixed sugars via 5-hydroxymethyl furfural (HMF) and furfural intermediates. To achieve this goal, we must first convert glucose and xylose to HMF and furfural in favorable yields. Current processes to produce HMF/furfural generally involve the use of acid catalysts in biphasic systems or solvents such as ionic liquids. However, the yield from transforming glucose to HMF is lower than the yield of furfural from xylose.ResultsIn this study, we present an efficient chemical pathway simultaneously transforming glucose and xylose to HMF and furfural via ketose intermediates, i.e., fructose and xylulose, which were generated from glucose and xylose via enzymatic isomerization. In the enzymatic isomerization, by adding sodium borate to complex with the ketoses, xylose conversion reached equilibrium after 2 h with a conversion of 91% and glucose conversion reached 84% after 4 h. By enzymatically isomerizing the aldoses to ketoses, the following dehydration reactions to HMF and furfural could be performed at low process temperatures (i.e., 110–120 °C) minimizing the side reactions of the sugars and limiting the degradation of furfurals to humins and carboxylic acids. At 120 °C, pH 0.5, and 15 min reaction time, mixed ketose sugars were converted to HMF and furfural in yields of 77% and 96%, respectively (based on starting aldose concentrations).ConclusionTaken together, our results demonstrate that this combined biological and chemical process could be an effective pathway to simultaneously convert biomass-derived glucose and xylose to HMF and furfural, for use as intermediates in the production of hydrocarbons.

Borohydride in ionic liquids for tailored hydrogen release

H2 as an environmentally benign energy carrier could answer the world's continuously increasing demand for sustainable energy sources, especially in portable fuel cell applications. Thereby, H2 storage is the key issue. In the present work, we developed a liquid H2 storage material based on BH4− and ionic liquids for tailored H2 release under ambient conditions using various catalysts as releasing agents. Thereto, we synthesized four BH4− ionic liquids via ionic exchange. The most promising BH4− based ionic liquids are 1-Ethyl-3-methylimidazolium BH4− and 1-Propyl-3-methylimidazolium BH4−, containing up to 3 wt% releasable hydrogen and the latter being liquid at standard temperature. The hydrolysis of 1-Ethyl-3-methylimidazolium BH4− with various supported metal catalysts (Pt/C, Pt/CNT, Ru/CNT, Pd/CNT, 5 wt% metal) and H2O (8, 16, 24 eq.) was assayed. The highest yield was obtained with 24 eq. H2O and Pt/CNT. The catalysts were characterized via X-ray photoelectron spectroscopy and transmission electron microscopy/energy-dispersive X-ray spectroscopy. To calculate the catalyst activities, the dispersion and size distribution of the metal particles were determined. Recycling of Pt/CNT showed a reasonable stability of the catalyst activity over four recycling runs. In order to avoid spontaneous crystallization of 1-Ethyl-3-methylimidazolium BH4− as a storage material, 1-Propyl-3-methylimidazolium BH4− was introduced. The hydrolysis yield was significantly increased by the use of acidic catalysts, such as HCl and Amberlyst 36. Further enhancement of the H2 yield was achieved by adopting a semi batch process, continuously adding 1 M HCl to 1-Propyl-3-methylimidazolium BH4−. The H2 release correlated approximately linearly with the acid addition rate, excluding liquid-liquid mass transfer limitations during the hydrolysis. Based on 11B NMR analysis, a reaction mechanism of the hydrolysis of BH4− ionic liquid with HCl as catalyst is proposed.

Solubilized Carbohydrate Production by Acid‐Catalyzed Depolymerization of Cellulose in Polar Aprotic Solvents

AbstractThis paper explores the effectiveness of several polar aprotic solvents, including 1,4‐dioxane, ethyl acetate, tetrahydrofuran (THF), methyl iso‐butyl ketone, acetone, acetonitrile, and gamma‐valerolactone (GVL), in depolymerizing cellulose into solubilized carbohydrates in the presence of acid catalyst. Whereas the yields of solubilized carbohydrates were strongly dependent on the polar solubility parameters of solvents, the use of acid catalyst substantially eliminated differences in the yields for the various solvents, which were in the range of 83–97%. The yields of levoglucosan and solubilized carbohydrates from cellulose in 1,4‐dioxane, THF, and acetone approached that of GVL, almost completely solubilizing cellulose within 1–7 min. Low initial rates of levoglucosan degradation caused these low polarity, low boiling point solvents to exhibit high stability and competitive yields of the anhydrosugar compared to high polarity and high boiling solvent such as GVL. The ease of recovery of low polarity, low‐boiling solvents makes them attractive media for production of solubilized carbohydrates, which the use of acid catalyst makes possible.

The Effect of Catalyst in the Process of Nano-Silica Particle Formation as a Hydrophobic Material

<p>Nano Silica is known as a hydrophobic material used to coat the material that further modifies the surface properties of the material. In this study the process of making nano silica material is using sol-gel method. The sol gel process is defined as the process of forming an inorganic compound through chemical reaction in solution at a low temperature wherein the process a phase changes from the colloidal suspension (sol) to a continuous liquid phase (gel). The types of catalyst were studied. The result was then applied to cotton, polyamide and silk fabrics. Acid catalyst showed the greatest moisture reduction based on Moisture Content and Moisture Regain evaluation in cotton and polyamide fabrics, whereas base catalysts showed a significantly less moisture reduction on the three fabrics. The use of these types of catalyst will also affect the value of the tensile strength of each fiber. Tensile test results showed that the use of acid catalysts decreased the maximum tensile strength in cotton fabrics by 88.57%, compared to polyamide and silk fabrics and the use of base catalyst showed less significant decreased on tensile strength for all fabrics.</p>

Catalytic upgrading of bio-oil in hydrothermal liquefaction of algae major model components over liquid acids

We selected acetic acid and sulfuric acid as liquid acid catalysts to investigate their performance on hydrothermal liquefaction (HTL) of algae major model components, including polysaccharides, proteins, lipids, and polysaccharides-proteins mixture. The aim of this study was to understand the catalytic effects of liquid acid catalysts as well as the formation process mechanisms and properties of the bio-oils from HTL of algae. We also used the two acids in HTL process of Chlorella vulgaris to estimate their catalytic performances in algae and compare this performance with the results from HTL of model components. Product distributions from different catalytic conditions were compared with blank results. Bio-oils were analyzed by elemental analysis, gas chromatography-mass spectrometry (GC–MS), and thermal gravimetric analysis (TGA). The results showed that the addition of acetic acid or sulfuric acid had no positive effect on the enhancement of bio-oil yield from HTL of individual algae major model components; however, the use of liquid acid catalysts could prevent the detrimental effect of interaction between polysaccharides and proteins on bio-oil yield. H/C ratios and higher heating values (HHVs) of bio-oils obtained from HTL of algae major model components increased significantly in the presence of acid catalysts. Sulfuric acid favored the oxygen removal process, and acetic acid reduced the nitrogen content in bio-oil from HTL of proteins. GC–MS results showed that bio-oil composition was greatly altered when adding acids. The light component proportion of catalytic upgraded bio-oils was significantly higher than that of bio-oils obtained with no catalyst. The results of HTL of Chlorella vulgaris with acid catalysts indicate that both acids favor to the hydrolysis of cellulose; therefore, the use of acid catalysts could accelerate the formation of bio-oil from cellular components. The difference between the HTL of algae major model components and real algae using acid catalysts was probably due to the complexity of algae structure.

Comparison of three methods for the methylation of aliphatic and aromatic compounds.

Methylation protocols commonly call for acidic, hot conditions that are known to promote organic 1 H/2 H exchange in aromatic and aliphatic C-H bonds. Here we tested two such commonly used methods and compared a third that avoids these acidic conditions, to quantify isotope effects with each method and to directly determine acidic-exchange rates relevant to experimental conditions. We compared acidic and non-acidic methylation approaches catalyzed by hydrochloric acid, acetyl chloride and EDCI (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide)/DMAP (4-dimethylaminopyridine), respectively. These were applied to two analytes: phthalic acid (an aromatic) and octacosanoic acid (an aliphatic). We analyzed yield by gas chromatography/flame ionization (GC/FID) and hydrogen and carbon isotopic compositions by isotope ratio mass spectrometry (GC/IRMS). We quantified the 1 H/2 H exchange rate on dimethyl phthalate under acidic conditions with proton nuclear magnetic resonance (1 H-NMR) measurements. The δ2 H and δ13 C values and yield were equivalent among the three methods for methyl octacosanoate. The two acidic methods resulted in comparable yield and isotopic composition of dimethyl phthalate; however, the non-acidic method resulted in lower δ2 H and δ13 C values perhaps due to low yields. Concerns over acid-catalyzed 1 H/2 H exchange are unwarranted as the effect was trivial over a 12-h reaction time. We find product isolation yield and evaporation to be the main concerns in the accurate determination of isotopic composition. 1 H/2 H exchange reactions are too slow to cause measurable isotope fractionation over the typical duration and reaction conditions used in methylation. Thus, we are able to recommend continued use of acidic catalysts in such methylation reactions for both aliphatic and aromatic compounds.

Base-Promoted Three-Component One-Pot Approach to 3-(α,α-Diarylmethyl)indoles via Arylation of 3-Indolylalcohols

A base-promoted 3-component one-pot approach to 3-(α,α-diarylmethyl)indoles via arylation of in situ generated 3-indolylalcohols in ethanol–water solvent system is reported. Use of acid catalysts or neutral organocatalysts does not offer the desired product, but furnish bis(indolyl)methanes instead. Electron-rich aromatics such as naphthols and phenols are preferably employed for arylation. The atom economy, use of green solvent, and the multicomponent strategy are the notable features of the reaction.

Development of Cutaneous Bioadhesive Ureasil-Polyether Hybrid Films

The hydrolysis and condensation reactions involved in synthesis of ureasil-polyether films influence the film formation time and the number of chemical groups able to form hydrogen bonds, responsible for the bioadhesion, with the biological substrate. The objective of this work was to study the influence of the use of an acid catalyst (hydrochloric acid) and a basic catalyst (ammonium fluoride) in the hydrolysis and condensation reactions on the time formation and bioadhesion of ureasil-polyether films. The toxicity of the films was evaluated. The MTT assay has shown cell viability of human skin keratinocytes higher than 70% of all analyzed materials suggesting low cytotoxicity. The bioadhesion of the films is strongly dependent on the viscosity and hydrophilic/hydrophobic balance of the polyether chains used to synthetize the hybrid molecules. The use of acid catalyst promotes the formation of less viscous films with higher bioadhesion. The hybrids formed by more hydrophilic PEO chains are more bioadherent, since they can interact more efficiently with the water present in the stratum corneum increasing the bioadhesion. Due to their low toxicity and high bioadhesion, the ureasil-PEO films obtained by using HCl as catalyst agent are good candidates for application to the skin as bioadhesive films.

Peluang dan Tantangan Komersialisasi Biodisel-Review

Hydrogen is one of the environmentally friendly fuel, however hydrogen is not always available due to continuously increasing energy demand and fossil fuel availability become more limited. Gap between demand and supply is essential to find alternative fuels. Biodiesel could be a substituent for fossil fuels, especially for hydrogen. Biodiesel could be made by mixing vegetable oils or fats with fossil fuel with a ratio of (5-20) wt.% however in a long time effect of this mixture can damage the engine. To overcome the problem, biodiesel can be synthesized via transesterification of oil and alcohol with the aid of acid or base catalyst to produce glycerol and FAME (Fatty Acid Methyl Ester). Challenges faced for the commercialization of biodiesel among others, (1) expensive raw material (edible oil), (2) reaction time and separation of the relatively long time (minimum 15 hours), (3) the use of acid catalysts still leaves the problem of corrosion and corrosion of machine tools and pollution to the environment by the catalyst. To make biodiesel competitive in the market, used oil (waste cooking oils, WCO), agricultural waste, and recent studies using microalgae could be used as source of biodiesel production. To shorten the reaction time, reaction was carried out using ultrasonic reactor technology and to minimize environmental pollution to use the solid catalyst. This paper will summarize on the adoption of latest technologies in producing biodiesel from used frying oil and microalgae.

ChemInform Abstract: Advancements in Solid Acid Catalysts for Biodiesel Production

AbstractReview: 150 refs.

Biodiesel production using 4-dodecylbenzenesulfonic acid as catalyst

The synthesis of biodiesel from triglycerides and methanol using 4-dodecylbenzenesulfonic acid as catalyst was studied. The use of acid catalysts in the production of biodiesel has the advantage that in addition to accelerating the transesterification of triglycerides, they also catalyze the esterification of free fatty acids and, moreover, they do not form soaps or emulsions. Regarding the 4-dodecylbenzenesulfonic acid catalyst used in this work, it has a further advantage in that it has a hydrophobic moiety in its molecular structure, which permits a much higher transesterification rate than that of other acid catalysts and, hence, conversions higher than 95% can be attained under mild reaction conditions in less than 3h.From the results of a first set of experiments, an empirical model was calculated that related the values of conversion, at 3h of reaction, and the values of the influencing factors quantitatively. From this model, it was found that the effects of temperature and the catalyst/oil molar ratio meant that the higher the values of any of these factors, the higher the conversions obtained. Conversely, methanol proved to be an obstacle at low conversions because it slowed down the reaction. However, under high temperature and/or high proportions of catalyst, (i.e., for conversions >80%), higher proportions of methanol also favored higher conversions.A second set of experiments was also carried out at 80 and 90°C and from the joint analysis of the results of all experiments performed in this work (first and second sets) it was observed that the transesterification kinetics reflected a first-order reaction, with an activation energy of 66.3kJ/mol. At 90°C it was possible to obtain conversions higher than 98% in less than 2h.

Optimization of rapeseed oil fatty acid esterification with methanol in the presence of sulfuric acid

Abstract The interest in biodiesel production from low cost feedstocks is still increasing. Such feedstocks usually contain large amounts of free fatty acids, which make the currently employed base catalysts inefficient, thereby promoting the use of acid catalysts. Due to the high activity and low cost, sulfuric acid could become the most widely used acid catalyst for biodiesel production. Research undertaken so far using sulfuric acid for esterifi cation of fatty acids has shown that the products obtained fail to meet the requirements of the standard EN 14214. This paper describes a systematic study of rapeseed oil fatty acids esterification in order to obtain a product complying with the standard EN 14214. The influence of sulfuric acid concentrations (0.1-3.0%), methanol molar ratios (1:1-20:1) and reaction time (0-360 min) was evaluated. Finally, a two-stage esterification process was developed, where in optimal conditions esterification yield of 97.8% and ester content of 99.6% were achieved.

A novel CO2-selective synthesized amine-impregnated cross-linked polyvinylalcohol/glutaraldehyde membrane: fabrication, characterization, and gas permeation study

In this paper, polyvinyl alcohol (PVA) membranes impregnated with amines (monoethanolamine and diethanolamine) were prepared for CO2/N2 separation. The cross-linking of DEA impregnated PVA by glutaraldehyde (GA) with different mass ratios (GA/PVA: 0.5, 1, 3, 5, 7%) were investigated with no use of acid catalyst or organic solvents. The effects of the amine type-concentration, cross-linking agent content, and feed pressure as well as stability were examined in both pure and mixed gases. Generally, CO2/N2 performance through the DEA-PVA membranes was higher than that of MEA-PVA membranes. The fabricated membranes were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The cross-linked membranes showed reasonable CO2/N2 permselectivities in comparison with uncross-linked membranes and these are recommended for high performance membrane for CO2/N2 separation. The best-yielding membranes (DEA-PVA/GA(1 wt%)/PTFE) represented the greatest CO2/N2 selectivity of 122.04 and 907.06 for pure and mixed gas experiments, respectively.

Kinetic study of the dehydration of d-xylose in high temperature water

A kinetic model of the homogeneous conversion of d-xylose in high temperature water (HTW) was developed. Experimental testing evaluated the effects of operating conditions on xylose conversion and furfural selectivity, with furfural yields of up to 60% observed without the use of acid catalysts. The reaction order for the decomposition of d-xylose was assumed to be above two, while the conversion of d-xylose to furfural and the degradation of furfural were first order reactions. Estimated kinetic parameters were within the range of values reported in the literature. The activation energy of furfural production showed that the ionization rate was high enough for HTW to replace acid catalysts. Simulated results from this model were in good agreement with experimental data, allowing the model to aid reactor design for the maximization of productivity.

P-145 酸触媒を用いた超臨界水ガス化における反応特性の検討(ポスター1,ポスター発表)

P-145 酸触媒を用いた超臨界水ガス化における反応特性の検討(ポスター1,ポスター発表)